1. Technical Field
The present invention relates to the loading and unloading of flowable cargo transported in lined or unlined bulk cargo containers. In particular, it relates to mobile discharge devices which unload containers on level surfaces by moving through the container under power and discharging cargo without having to raise the container.
2. Background Art
Transportation of containers for bulk commodity products (grains, etc) have been implemented using a variety transport vehicles, such as trucks, railroads, and ships. An important economic factor in the transportation of bulk commodities is the speed and ease with which the commodities are loaded onto and unloaded from the container.
Typical methods of loading and unloading tank type containers are pressure systems such as pumps to force commodities into the container during loading and to provide suction to remove the commodities during unloading. Another popular method is the use of gravity mechanisms. For example, gravity may be used to unload a dry box ISO container by tilting the container such that the bulk commodity flows toward a discharge door at the rear end of the container.
The prior art approach of raising the container to allow the bulk commodity to flow out has been effectively used to unload cargo from the container with a minimum amount of labor cost. With this method, there is some additional labor expense of manually removing the residual commodity trapped in the corners. In addition to the labor expense required to remove the residual commodity product from the corners, the economic efficiency of the container and transport vehicle is reduced due to the delay involved with this additional step in the unloading procedure. More important, the capital or rental cost of the mechanism required to lift the weight of the container for tilting purposes is high, and also raises safety problems inherent in any machinery of that size. Further, due to its cost, this type of unloading device is not always available. In the case where bulk commodity is infrequently delivered, this type of unloading solution may not be available or economically feasible.
Another prior art approach which addresses the foregoing problem is to unload the cargo by having an individual manually control a suction hose, and walk through the container to unload the contents. This solution allows unloading the cargo in locations where tilt mechanisms are unavailable. However, it also entails several drawbacks. It is very labor intensive, and due to the weight involved, must be done at a speed which allows an individual to safely unload the container contents. In turn, this increases unloading time and reduces economic efficiency. In addition, it requires that the individual enter the container which exposes products to contamination by the worker, and depending on the cargo, exposes the worker to contamination as well.
A third alternative is to unload the commodity using a vehicle such as a small front loader which can be driven into the container. This method is quicker than the manual method discussed above, but is much costlier due to the cost of the front loader. In addition, the likelihood of contamination of the cargo is an inherent drawback. The labor costs may also be higher since the front loader operator may be better paid than the manual laborer discussed above. Depending on the commodity, the front loader solution may not be usable for all types of cargo. In addition, the front loader is an expensive item of equipment which may not be available at a given location just as the tilt mechanism may not be available.
While addressing the various aspects of unloading bulk commodities in container systems, the prior art has typically chosen alternative methods such as the tilt systems or manual systems discussed above. While tilt systems can rapidly unload, they have numerous drawbacks such as high cost, non-universal availability, and safety concerns. On the other hand, manual systems are slower to unload, have a potentially high contamination risk, and are less efficient than tilt systems. Front loaders are also less efficient than tilt systems, but retain the aspect of high cost. The prior art has not provided an unloading system which is universally available, does not have the high cost of tilt systems and front loaders, or the economic inefficiency of manual systems, reduces worker exposure to physical injury, reduces worker exposure to contamination by the cargo, and cargo exposure to contamination by the worker.